1. Field of the Invention
The present invention relates to a one-wire bus for serial data communication. More particularly, but not by way of limitation, the present invention relates to an apparatus and method to enhance the operation of a one-wire bus such that known data may be inserted into a data stream communicated on the bus.
2. Background of the Invention
Serial data communication schemes are well known in the art. One subset of such schemes comprises single-wire, half duplex communication schemes wherein master and slave devices may engage in the bidirectional exchange of digital information over a single channel. One particular scheme is the single-wire data bus which is the subject of U.S. Pat. Nos. 5,761,697 issued to Curry et al.; 5,210,846 issued to Lee; 5,809,518 issued to Lee; 5,864,872 issued to Lee et al.; and 6,108,751 issued to Lee. Essentially, a variation of this communication scheme has found its way into a number of commercially available semiconductor parts such as the iButton® series produced by Dallas Semiconductor of Dallas, Tex.
While this single-wire communication scheme has proven to be both inexpensive and effective as a means for the exchange of information between electronic components in a system, there is presently no method for substituting known data into the single-wire data stream. The insertion of known data into a data stream is useful for system debug, testing, software development, and the like.
In addition, as the number of devices offering a single wire interface has expanded, a need has arisen to allow device substitutions. For example, a group of smaller memory devices could be used to emulate a larger memory device or, conversely, a large memory device could be used to emulate a group of smaller devices. Presently there is no provision for such substitutions.
Yet another limitation of the one-wire bus arises when using EPROM devices. If such devices are to be programmed, voltages are required on the one-wire bus which are incompatible with other types of devices.
It is thus an object of the present invention to provide a device which can transparently insert known data into a data stream on a one-wire bus.
It is further object of the present invention to provide a method for the insertion of known data into a data stream on a one-wire bus.
It is still a further object of the present invention to provide modification of the data stream on a one-wire bus such that various slave device types may be substituted transparently to the master such that the substituted devices appear to the master as a different device or as different devices.
It is yet a further object of the present invention to simultaneously provide an unprotected one-wire bus suitable for EPROM devices and a protected one-wire bus suitable for all devices such that both buses appear to the master as a single one-wire bus.